Methods of manufacturing arsenate of lead



AUSTIN 0. ALLEN, OF MERCHANTVILLE, NEW JERSEY, ASSIGNOR. T0 i 1- C0. 1N0, G1 PHILADELPHIA. PENNSYLVANIA, A CORFOBATION O}? EEENNSKL- VANIA.

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I/IE'IHODS MANUFACTURING AIRSENATE 0F LEAD.

No Drawing.

To (NZ 10. 1 0m may/ can (er a 1 3e it known that I. iuts'rix i Annex, a citizen of the United States. residii'ig in Merchantville, New Jersey, have invented certain improvements in li'iethods ot Marlin 't'acturiug Arsenate of head, of which the t'ollowin;- is a specification.

The object of my invention is to provide an economical method tor the imlnu'l'acture ol' arseuate o't' lead in the. form oi" aeid arsenate of lead (lhllkstl having certain physical properties which render it most suitable tor use as an insecticide tor the ex termination of external lea'l eating insects.

ilrsenate of lead isin extensive and growing demand as an. exterminator o't external lea t' airing;- insects which are destructive to plantlit'e. it is an established i'act that arsenate oil lead of the formulae lhlli xstl is a quicker and stronger poison than normal arseuate ot lead ot the tormulae (Phi (Astlqh. l urtliermoro tor most ell'eetive and economical results, an arsenate of lead must be very light and llutiy in order to insure even distrilaition when used either as a wet spra vin; or dry dusting material, and also should he composed ot' exceedingly line part ieles so that the individual particles may become lodged in the minute indentations ol' the surl'ace o'l fruit or foliage.

l3 v means ot my present inventiom I am permitted to manufacture a pure acid arsenate. oi lead or as it is technically knowin di-arsenate oi lead, poss ssing physical properties reiulering it ideal tor use as an insecticide. My acid arsenat'e of lead 'lurther tree from soluble salts, making possible the use therewith oi various types of Spreaders, since there are no appreciable percentages oi soluble salts or tree litharge present to enter into combination with them and do; stroy their "Function as spreaders. turthermore am enabled to recover and make use. oi" i raictically all acids liberated in the process, which makes my method an extremely economical one.

3. have found that when arsenate of lead manufactured from basic acetate of lead,

Specification of Letters Patent.

1921. Serial No. 481,208.

oi l ad imnurl'actured from nitrate of lead,

while it is a pure acid arsenate of lead, does not have the desired physical properties.

I have discovered that an acid arsenate of lead oi the desirable physical properties may he nianulactured when the arsenate of lead is precipitated from a basic solution of acetate of lead and nitrate of lead with arsenic acid, under certain definite conditions and tl at by the use of definite percentages of basic acetate of lead and nitrate of lead in the. solution from which I precipitate the arsenate of lead with arsenic acid and with a definite dilution, temperature and time of precipitation, extremely desirable results are obtainable in the manutacture of a product having ail the qualities of the ideal insecticide.

1n carrying out my invention, make use of straight chemical reactions, no catalyzer or material toreign to the reaction being employed, and I have found that the follow ing proportions of materials and mode of procedure will furnish excellent results:

In a tank of suitable size (about 3000 gallons capacity) provided with an agitator. 1 place about 2000 gallons of water, and add to the water 165 lbs. of acetic acid,'

which amount of acid is sutficient to convert 640 lbs. 0t lit-barge into trl basic acetate acetic acid, nitric acid of lead in accordance with the following rez'iction. 3Phti-lilitl lhath;

then add 16.5 lbs. of 40 Baume nitric acid, a lowed by 6&0 lbs. oi lithar c added while agitator is in. operation, The batch is new heated to 120 F, preferably with live steam, and as soon as all the litharge is coned to lead salts, which point can easily be detected by the milky appearance of the solvtion and the absence of yellowish tinge to the presence of litharge, I add 515 )s. of arsenic acid, approximately 63% i 7),, said acid being added very slowly. Approximately one hour is consumed in. adding the entire amount of the arsenic acid. The batch is now allowed to agitate i'or twenty five, minutes, after which a sample of the filtrate is tested for the presence of lead salts and arsenic acid. For the proper balance, the filtrate should show a very slight trace of lead salts and no arsenic acid, and the desired point can easily be reached by the addition 01" small amounts of litharge or arsenic acid, as may be necessary. W'hcn the material is properly balanced, it is pumped into any desired washing type of filter press and is thoroughly washed, the first part of the wash Water being run into the tank with the filtrate until the-total volnine is approximately 2000 gallons. The ca'lres o'l arsenate of lead are then taken from a the press, dried and pulverized.

The filtrate from this batch containing and small quantities of acetate of lead and nitrate of lead is now pumped into the orecipitating tank. Practice has shown that there will be a loss of approximately 3% of the acetic and nitric acids. To this amount, approximately five acetic acid and one-halt 1b. of 20 Baum .n tric acid is added, followed by Gail) lbs/of ,li'tharge, which latter is added while the agitator is running. The temperature is then raised to 120 F., and the process continued as described above. The process thus becomes continuous, and the loss is very small.

The reactions involved in the process are as follows:

The pure acid arsenatc of lead oi fine azrpee lluliy physical properties is made as I have shown above by precipitating arsenate of lead from a basic solution of lead acetate and badniiratc with arsenic acid, when the percentage of lead nitrate is just sulficient to insure the. formation of a pure acid arscnatc o'l lead. The volume in which I precipitate and the temperature and rate of pre :ipitation greatly aid in forming theproduct.

tion of the lead salts of acetic acid and nitric acid, which acids were used in forming the solution in vthe ratio of approximately parts of 70%, acetic acid to 1 part of 40 Baunu'i or ($1.97, nitric acid, with arsenic acid of approximately 58 to 63% As' tl, con tent, at a tcmperaturepf approximately 120 F,

3. The method of manufacturing acidarsenate of lead, which consists in precipitating the arsenate of lead 'iT I m,,3 b9.SlC solution oi the lead salts of acetic and nitric' acid, which acids were used in forming the solution in the ratio ofilO parts of 70% acetic acid to 1 part oi. 40 Baum 'or (51.9% nitric acid, with arsenic acid of 58% to 63% As. content, said precipitationtaking place.in ,.a dil .ition I by weight of ater for each lfparhby weight-of the dry, arscnate of lead precipitate. i Y

4. 'lhemcthml of maiuifacturing acid arsenate of lead, which consists in precipitat mg the arson-ate oi load from a basic solution of the lead salts oi acetic'acid and nitric acid, such acids being used in solution in the ratio of 10 parts of 70.9 acetic acid and 1. part 40 Baum or 61.9% nitric acid, with arsenic acid of approximately 58",, to (33% the filtrate AUs'rin o. ALLEN.

otapproximately 16 parts preparing the /\s,() content, charging and washings with suiiicient' acet c acid and nitric acid in the ratio of 10. 

